The invention relates to the forming of cylindrical metal tubular articles which are suitable for use as seamless photoconductive substrates. More particularly, the invention is directed to an improved method of forming an elongated, relatively thin-walled cylindrical tube from an annular work piece of considerably greater thickness by the simultaneous reduction of wall thickness and elongation of the tube.
A method of simultaneously reducing the internal diameter of a tubular work piece while lengthening the tube is taught by Ernestus, in U.S. Pat. No. 3,222,905. As disclosed therein, a cylindrical work piece is supported within a die ring in encircling engagement with its outer surface and the combination rotated while a stationary forming tool within the work piece reduces the internal diameter. Further, the forming tool comprises a series of rollers which are adjusted in a fixed position relative to the work piece. This invention is directed to an improvement of the method taught by Ernestus.